The recognition of continuous roadway illumination, also referred to below as “city recognition,” is essential for the development of high-beam assistants. With (adaptive) high-beam assistants the headlights must not be turned up when there is continuous roadway illumination. Accordingly, illuminated roadways in suburban areas must also be recognized. Instead of “recognition of continuous roadway illumination,” for simplification the term “city recognition” is used. Such city light recognition is disclosed in German Published Patent Appln. No. 10 2009 028 342. German Published Patent Appln. No. 10 2009 028 342 describes a method for determining whether an area is illuminated. The method evaluates image data of a camera. The area is assessed as illuminated if at least two stationary roadway illumination units are recognized based on the image data, and these roadway illumination units have a spatial distance from one another.
The basis of city recognition is the detection of multiple streetlights within a certain distance. As soon as at least two streetlights have been recognized for a certain time (distance), a “city signal” is generated and the headlights are turned down. Switching over too early into the city mode (i.e., dimming the light or lowering the light cone or light emission range in the direction of the roadway) is prevented by evaluating the vertical position (detection angle) of the streetlight in the image.
In contrast, the headlights are not automatically turned down at crosswalks and illuminated intersections.